I believe the benefit is that you can get better coverage because the fog that is created will go Into all the nooks in between branches and leaves. When using a normal sprayer, the particles are large and will fall with gravity, it will not wind it's way inbetween thick foliage. If you are spraying something that needs direct contact to kill your target bad bug, you may miss much of the surface area of the plant with a normal sprayer. I believe the atomizer sprayer is also very efficient with its use of whatever you are spraying.
Simon